The rise followed the group's confirmation, in a short statement on Monday, "that it is currently holding discussions about possible combinations or transactions".

While OCI made no mention of any potential deal partner, CF Industries on Monday said that it was "in preliminary discussions with OCI regarding a potential combination involving certain of OCI's businesses".

Complementary strategies?

A deal between CF Industries and OCI would appear to offer notable scope, given the groups' strategies of geographical expansion in nitrogen fertilizers.

CF Industries has long had an eye on expanding in the important European nutrient market, last year entering failed merger talks with Norway's Yara International, the world's biggest nitrogen producer.

Earlier this month, CF bought Yara out of their $1.3bn UK-based GrowHow fertilizer joint venture – surprising many investors given that Yara, given its far stronger position in Europe, was considered the natural acquirer.

By contrast, OCI has sought to expand in the US to exploit cheap shale gas, a key raw material for nitrogen fertilizer plants (although some use coal as an alternative).

OCI in April underlined that its "strategy is focused on growing our nitrogen fertilizer and industrial chemicals production capacity by capitalizing on natural gas monetization opportunities in the US where we have taken a view on the long-term sustainability of low natural gas prices".

The group is expecting later this year to open a nitrogen plant in Iowa with capacity for producing 2.43m tonnes of chemicals a year, including 2.11m tonnes of nitrogen fertilizers.

Dutch shift

However, any significant tie-up between the two groups would need to overcome the substantial interest, of more than 50%, that the Sawiris family members have in OCI, which is part of their Orascom telecoms-to-construction empire.

OCI, short for Orascom Construction Industries, only moved its listing from Cairo to Amsterdam two years ago after a tax dispute with Egypt's former government following the 2011 revolution.

OCI four months ago demerged its engineering and construction business to become a specialist nitrogen and chemicals group.

Growing empire

OCI's biggest existing plant is in fact in the Netherlands, with capacity of 2.35m tonnes of chemicals a year, including 2.15m tonnes of nitrogen fertilizers.

But the group also owns two plants in Egypt and one in Algeria, besides two further sites – one being expanded and the other, a methanol producer, set to open next year – in the US.

OCI expects to have production capacity for 12.1m tonnes of chemicals by the end of 2016, including 8.91m tonnes of nitrogen nutrients, up from figure of 7.69m tonnes and 6.76m tonnes respectively as of last year.

Late on Friday, when reports of a CF-OCI deal emerged, CF Industries shares closed up 9.9% at $68.92 in New York.

Faced with mounting concerns over labour shortages and fears they may not be able to fulfil retailer contracts, some British growers have sought to cut ties with UK supermarkets in favour of companies elsewhere in Europe.

Manufacturers of crop protection products are stockpiling agrochemicals in warehouses in a bid to keep input costs down for farmers after Brexit, according to the chief executive of the Crop Protection Association, Sarah Mukherjee.